44 IMPORTED PARASITES. 



Europe, and the small quantities of gypsy and brown-tail pupae 

 which were received in 1906 and 1907 from those countries 

 where it was most abundant made any attempts to investigate 

 its life and habits difficult of execution. The females would 

 never evince any interest in gypsy or brown-tail pupae in the 

 laboratory, and all of the many reproduction experiments which 

 were made failed utterly. This was subsequently found to be 

 due to the fact that their eggs were undeveloped, and it was not 

 until a careful series of microscopic dissections were made that 

 this insuperable obstacle to success was discovered. 



In 1908 the same importation of gypsy moth pupae from Italy 

 which served to establish the host relations of Chalcis served 

 also to establish the primary character of the parasitism by 

 Monodontomerus. It was reared from the gypsy moth pupffi 

 direct, and in such numbers as to indicate that it was a parasite 

 of considerable importance; and great regret was felt that it 

 had not been liberated in larger numbers upon the first oppor- 

 tunity. It was hardly considered probable at that time that 

 the small number liberated during the early spring of 1906 

 would succeed in establishing themselves. 



In the winter of 1908-09, large numbers of the hibernating 

 nests of brown-tail were collected from various localities, as they 

 had been each winter since the beginning of the work, and from 

 these nests issued a very few hibernating females of Monodon- 

 tomerus, exactly as they had previously issued from nests simi- 

 larly collected in Europe. The circumstance was as unexpected 

 as it was gratifying, and indicated that the parasite had mul- 

 tiplied rapidly in the field, because similar collections of even 

 larger quantities of brown-tail nests had not produced the para- 

 site the year before. Steps were immediately taken to determine 

 the distribution of the parasite, and the surprise was greater 

 when it was discovered to be sparingly but generally dis- 

 tributed over an area of approximately 500 square miles, ex- 

 tending in nearly every direction, but farthest to the west, from 

 the original point of liberation. 



In the summer of 1909, when the proper season had arrived, 

 it was recovered for the first time as a parasite of the gypsy moth 

 in the field. Although it was not very common, it was found to 

 be generally distributed, exactly as indicated by the collections 



